A high volumetric efficiency combination gear pump

Abstract

The application discloses a high-volume-efficiency combined gear pump and relates to the technical field of gear pumps.The combined gear pump comprises a gear pump shell, a gear pump end cover is connected to the upper end opening of the gear pump shell, a driving cycloid gear shaft is rotationally connected in the gear pump shell, a cycloid gear is arranged on the outer wall of the driving cycloid gear shaft, a driving gear is arranged on the outer side of the cycloid gear, the outer ring teeth of the driving gear are meshed with the outer ring teeth of a driven gear, upper side floating shaft sleeves are arranged at the upper ends of the driving gear and the driven gear, upper side oil pressing holes are arranged on the upper side floating shaft sleeves, lower side floating shaft sleeves are arranged at the lower ends of the driving gear and the driven gear, lower side oil pressing holes are arranged on the lower side floating shaft sleeves, an oil inlet and an oil outlet are arranged on the outer wall of the gear pump shell, a pre-pressing oil channel and a constant-pressure oil channel are arranged on the gear pump end cover, an overflow valve can be arranged between the pre-pressing oil channel and the constant-pressure oil channel, and the meshing and merging positions of the driving gear and the driven gear are communicated with the oil outlet.The combined gear pump has high volume efficiency and small pressure pulse.

Description

Technical Field

[0001] This invention relates to the field of gear pump technology, and in particular to a high-volume-efficiency combined gear pump. Background Technology

[0002] Hydraulic transmission technology has advantages such as high power density, flexible layout, and diverse control methods. It has been widely used in fields such as engineering machinery, metallurgy, mining, marine machinery and equipment, and petrochemicals. In recent years, it has also played a significant role in manned deep-sea diving, aviation, aerospace, navigation and other intelligent equipment. Among them, the hydraulic pump is the core component of the hydraulic transmission system and is the key to determining the performance of the hydraulic system.

[0003] Currently, hydraulic transmission technology is developing towards higher efficiency, lower noise, longer lifespan, greater integration, and greater intelligence. Gear pumps, as a representative of traditional hydraulic pumps, have promising application prospects due to their fewer parts and lower processing costs. However, while traditional gear pumps have simple structural designs and low costs, their requirements for power-to-weight ratio, efficiency, pulsation, and lifespan are not stringent, resulting in problems such as large pressure pulsation and low volumetric efficiency.

[0004] Therefore, there is an urgent need in this field for a high-volume-efficiency combined gear pump to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a high volumetric efficiency combined gear pump to solve the technical problems existing in the prior art. By using two pressurization steps, the volumetric efficiency can be effectively improved, and the oil discharge is more stable with less pressure pulsation.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention discloses a high volumetric efficiency combined gear pump, including a gear pump housing, a gear pump end cover connected to the upper opening of the gear pump housing, a driving cycloidal gear shaft rotatably connected inside the gear pump housing, one end of the driving cycloidal gear shaft extending out of the gear pump housing, a cycloidal gear provided on the outer wall of the driving cycloidal gear shaft, a driving gear provided on the outer side of the cycloidal gear, the cycloidal gear meshing with the inner ring teeth of the driving gear, the outer ring teeth of the driving gear meshing with the outer ring teeth of the driven gear, an upper floating bushing provided at the upper end of the driving gear and the driven gear, the upper floating bushing provided with an upper oil pressure hole, and a lower floating bushing provided at the lower end of the driving gear and the driven gear, the lower floating bushing provided with a lower oil pressure hole.

[0008] The outer wall of the gear pump housing is provided with an oil inlet and an oil outlet. The oil inlet can be connected to the lower pressure oil hole. Both the lower pressure oil hole and the upper pressure oil hole can be connected to the gap between the cycloidal gear and the driving gear. The gear pump end cover is provided with a pre-pressure oil passage and a constant pressure oil passage. An overflow valve can be provided between the pre-pressure oil passage and the constant pressure oil passage. The end of the pre-pressure oil passage away from the overflow valve is connected to the upper pressure oil hole. The end of the constant pressure oil passage away from the overflow valve is connected to the disengagement point of the driving gear and the driven gear. The engagement point of the driving gear and the driven gear is connected to the oil outlet.

[0009] Preferably, the lower end of the gear pump housing is provided with a shaft through hole, a connecting flange is provided at the shaft through hole, and the connecting flange is provided with multiple fixing threaded holes;

[0010] The outer side of the active cycloidal gear shaft is provided with a lip seal, and the inner side of the connecting flange is provided with a retaining ring groove. An elastic retaining ring is provided in the retaining ring groove, and the elastic retaining ring abuts against the lip seal.

[0011] Preferably, sliding bearings are provided between the active cycloidal gear shaft and the upper floating bushing, and between the active cycloidal gear shaft and the lower floating bushing.

[0012] Preferably, the gear pump housing and the gear pump end cover are fixed by a plurality of hexagonal head screws.

[0013] Preferably, the upper edge of the gear pump housing is provided with a housing sealing groove, and an end cap sealing ring is provided in the housing sealing groove.

[0014] Preferably, a lower sealing ring groove is provided on the bottom of the inner surface of the gear pump housing, and a lower irregular sealing ring is provided in the lower sealing ring groove;

[0015] The gear pump end cover has an upper sealing ring groove at its lower port, and an upper irregular sealing ring is provided in the upper sealing ring groove.

[0016] Preferably, an overflow valve mounting structure is provided between the pre-pressure oil passage and the constant pressure oil passage. The overflow valve mounting structure is used to install an overflow valve. Both the pre-pressure oil passage and the constant pressure oil passage are connected to the overflow valve mounting structure. The overflow valve mounting structure is also provided with an overflow pipe outlet and an overflow valve interface. An overflow pipe outlet plug can be detachably connected to the overflow pipe outlet, and an overflow valve interface plug can be detachably connected to the overflow valve outlet.

[0017] Preferably, a driven shaft passes through the center of the driven gear, and an axial channel is provided at the center of the driven shaft;

[0018] The gear pump end cover has an upper end face leakage oil passage on its inner top side. The upper end of the axial channel is connected to the upper end of the upper end face leakage oil passage. The gear pump housing has a lower end face leakage oil passage on its inner lower surface. The lower end of the axial channel and the lower pressure oil hole can both be connected to the lower end face leakage oil passage.

[0019] Preferably, both the upper floating bushing and the lower floating bushing have an oil suction groove on one side.

[0020] Preferably, the active cycloidal gear shaft and the cycloidal gear are an integral structure;

[0021] Alternatively, a pin may be perpendicularly inserted through the active cycloidal gear shaft, the inner ring of the cycloidal gear may have a groove, and one end of the pin may extend into the groove.

[0022] The present invention achieves the following technical effects compared to the prior art:

[0023] (1) The present invention has the advantages of high volumetric efficiency and low pressure pulsation. The inner ring teeth of the driving gear and the cycloidal gear of the driving cycloidal gear shaft form a cycloidal gear pump, and the outer ring teeth of the driving gear mesh with the driven gear to form an external meshing gear pump. The pressure oil output by the cycloidal gear pump overflows through the overflow valve, and the constant pressure oil enters the suction end of the external meshing gear pump, so that the suction end of the external meshing gear pump has a certain back pressure. After being pressurized, the high pressure oil finally output has less pulsation and sufficient oil suction, resulting in higher volumetric efficiency.

[0024] (2) The principle of this invention is simple and the structure is compact. The main body of the high volumetric efficiency combined gear pump consists of an active cycloidal gear shaft, a driving gear, a driven gear, an upper floating bushing, a lower floating bushing, a gear pump housing, a gear pump end cover, etc. The pre-pressurization method is simple and the arrangement structure is compact, and it can continuously and efficiently output high-pressure oil.

[0025] (3) The present invention can balance the force on the shaft of the active cycloidal gear. The inner ring tooth meshing oil discharge end of the active gear is radially opposite to the outer ring tooth meshing oil discharge end, which balances a certain radial unbalanced force.

[0026] (4) The driven shaft in this invention adopts a hollow shaft design. The internal leakage oil of the high volumetric efficiency combined gear pump is introduced into the axial channel through the leakage oil passage on the upper end face, and after merging, it is introduced into the lower pressure oil hole. The structure is compact and effectively outputs the internal leakage oil of the high volumetric efficiency combined gear pump, extending its service life. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a top isometric view of the high volumetric efficiency combined gear pump according to an embodiment of the present invention;

[0029] Figure 2 This is a bottom isometric view of the high volumetric efficiency combined gear pump according to an embodiment of the present invention;

[0030] Figure 3 This is a front view of a high-volume-efficiency combined gear pump according to an embodiment of the present invention;

[0031] Figure 4 This is a side view of a high-volume-efficiency combined gear pump according to an embodiment of the present invention;

[0032] Figure 5 This is a top view of the high volumetric efficiency combined gear pump according to an embodiment of the present invention;

[0033] Figure 6 This is a bottom view of a high-volume-efficiency combined gear pump according to an embodiment of the present invention;

[0034] Figure 7 This is a front sectional view of a high-volume-efficiency combined gear pump according to an embodiment of the present invention;

[0035] Figure 8 This is a side sectional view of the high volumetric efficiency combined gear pump according to an embodiment of the present invention;

[0036] Figure 9 This is an exploded view of the high volumetric efficiency combined gear pump according to an embodiment of the present invention;

[0037] Figure 10 This is a diagram of the internal parts of the gear pump housing in the high volumetric efficiency combined gear pump of this invention.

[0038] Figure 11 This is a top view of the meshing of the driving gear and the driven gear in the high volumetric efficiency combined gear pump of this invention.

[0039] Figure 12 This is a schematic diagram of the meshing structure of the driving gear and driven gear in the high volumetric efficiency combined gear pump of this invention.

[0040] Figure 13 This is a cross-sectional view of the gear pump end cover in the high volumetric efficiency combined gear pump of this invention.

[0041] Figure 14 This is a bottom cross-sectional view of the gear pump housing in the high volumetric efficiency combined gear pump of this embodiment of the invention;

[0042] Figure 15 This is a diagram showing the connection relationship between the active cycloidal gear shaft and the active gear in the high volumetric efficiency combined gear pump of this invention.

[0043] In the diagram: 1-Active cycloidal gear shaft; 2-Elastic retaining ring; 3-Lip seal; 4-Gear pump housing; 5-Lower floating bushing; 6-Driven gear; 7-Lower profile seal; 8-Hex socket head cap screw; 9-Upper floating bushing; 10-Overflow pipe outlet plug; 11-Overflow valve interface plug; 12-Upper profile seal; 13-Gear pump end cover; 14-End cover seal; 15-Active gear; 16-Pin; 17-Sliding bearing; 18-Oil inlet; 19-Oil outlet; 20-Oil suction groove; 21-Upper end face leakage oil passage; 22-Lower end face leakage oil passage; 23-Pre-pressure oil passage; 24-Constant pressure oil passage. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] The purpose of this invention is to provide a high volumetric efficiency combined gear pump to solve the technical problems existing in the prior art. By using two pressurization steps, the volumetric efficiency can be effectively improved, and the oil discharge is more stable with less pressure pulsation.

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] like Figures 1-15As shown, this embodiment provides a high volumetric efficiency combined gear pump, including a gear pump housing 4. A gear pump end cover 13 is connected to the upper opening of the gear pump housing 4, and the interiors of the gear pump housing 4 and the gear pump end cover 13 form a relatively sealed cavity. A driving cycloidal gear shaft 1 is rotatably connected inside the gear pump housing 4. One end (i.e., the lower end) of the driving cycloidal gear shaft 1 extends out of the lower end of the gear pump housing 4, and the lower end of the driving cycloidal gear shaft 1 is also connected to an external motor via a spline. A cycloidal gear is provided on the outer wall of the driving cycloidal gear shaft 1, and a driving gear 15 is provided on the outer side of the cycloidal gear. The inner ring teeth of the cycloidal gear and the driving gear 15 mesh to form a cycloidal gear pump. In addition, the outer ring teeth of the driving gear 15 mesh with the outer ring teeth of the driven gear 6, and the meshing of the outer ring teeth of the driving gear 15 with the driven gear 6 forms an external meshing gear pump. The upper ends of the driving gear 15 and the driven gear 6 are provided with upper floating bushings 9, and the upper floating bushings 9 are provided with upper oil pressure holes. Similarly, the lower ends of the driving gear 15 and the driven gear 6 are provided with lower floating bushings 5, and the lower floating bushings 5 ​​are provided with lower oil pressure holes. Both the upper floating bushings 9 and the lower floating bushings 5 ​​are figure-eight shaped structures, and will be provided with corresponding through holes for the driving cycloidal gear shaft 1 and the driven shaft on the driven gear 6. The upper oil pressure holes and the lower oil pressure holes are arc-shaped channels that run through the vertical direction.

[0048] The outer wall of the gear pump housing 4 is provided with an oil inlet 18 and an oil outlet 19. The oil inlet 18 is located below the oil outlet 19. Both the oil inlet 18 and the oil outlet 19 are threaded interfaces, used to connect pipe fittings to the hydraulic system. The hydraulic systems vary in different application environments, so they will not be listed here. Furthermore, the application technology and related devices of hydraulic pipe fittings are common knowledge and conventional techniques for those skilled in the art, so they will not be elaborated. The oil inlet 18 is an oblique hole, which can communicate with the lower pressure oil hole. Both the lower pressure oil hole and the upper pressure oil hole can communicate with the gap between the cycloidal gear and the driving gear 15. The gear pump end cover 13 is provided with a pre-pressure oil passage 23 and a constant pressure oil passage 24. An overflow valve can be provided between the pre-pressure oil passage 23 and the constant pressure oil passage 24. The end of the pre-pressure oil passage 23 away from the overflow valve is connected to the upper pressure oil hole. The end of the constant pressure oil passage 24 furthest from the overflow valve is connected to the disengagement point of the driving gear 15 and the driven gear 6. The engagement point of the driving gear 15 and the driven gear 6 is connected to the oil outlet 19. The specific locations of the disengagement and engagement points of the driving gear 15 and the driven gear 6 are as follows: Figure 11 For example, Figure 11 The oil outlet 19 is located at the upper end of the figure. At this time, the driving gear 15 and the driven gear 6 need to deliver hydraulic oil from bottom to top. The lower end is the disengagement point, while the upper end is the engagement point.

[0049] In actual use, low-pressure oil enters through the pipeline from the inlet 18 and flows into the lower pressure oil hole. It then flows upward from the lower pressure oil hole and enters the gap between the cycloidal gear and the drive gear 15, where it undergoes a first pressurization. The pressurized hydraulic oil continues to flow upward into the upper pressure oil hole, and then from the upper pressure oil hole into the pre-pressure oil passage 23. Subsequently, the hydraulic oil in the pre-pressure oil passage 23 flows through the relief valve into the constant pressure oil passage 24. The constant pressure effect of the relief valve ensures stable outflow oil pressure, thereby guaranteeing a small final output pressure pulse. The hydraulic oil flowing in from the constant pressure oil passage 24 enters the disengagement point of the drive gear 15 and the driven gear 6, and then flows from between the drive gear 15 and the driven gear 6 to the engagement point of the drive gear 15 and the driven gear 6, thereby completing secondary pressurization to improve volumetric efficiency. Finally, the hydraulic oil that has undergone secondary pressurization flows back into the hydraulic system from the oil outlet 19.

[0050] In this embodiment, the lower end of the gear pump housing 4 is provided with a shaft through hole, and a connecting flange is provided at the shaft through hole. The active cycloidal gear shaft 1 can pass through the connecting flange and the center of the shaft through hole in sequence and be rotatably connected with them. In addition, the connecting flange is provided with multiple fixing threaded holes, specifically four, which are located at the four corners of the connecting flange. By providing fixing threaded holes, the entire device can be fixed on a table or other flat surface.

[0051] Furthermore, a lip seal 3 is provided on the outer side of the active cycloidal gear shaft 1 to achieve sealing between the active cycloidal gear shaft 1 and the shaft through hole, thereby avoiding oil leakage.

[0052] In addition, a retaining ring groove is provided on the inner side of the connecting flange, and an elastic retaining ring 2 is provided in the retaining ring groove. The elastic retaining ring 2 is located on the lower side of the lip seal 3 and abuts against the lip seal 3. The purpose of setting the elastic retaining ring 2 is to prevent the lip seal 3 from moving axially.

[0053] In this embodiment, sliding bearings 17 are provided between the active cycloidal gear shaft 1 and the upper floating bushing 9, and between the active cycloidal gear shaft 1 and the lower floating bushing 5. By providing sliding bearings 17, sliding friction between the active cycloidal gear shaft 1 and the upper floating bushing 9 or the lower floating bushing 5 can be effectively avoided. Therefore, the material requirements for the upper floating bushing 9 and the lower floating bushing 5 are no longer stringent, which reduces costs to a certain extent.

[0054] Alternatively, the sliding bearing 17 can be omitted, allowing the outer side of the active cycloidal gear shaft 1 to directly slide and rub against the upper floating bushing 9 and the lower floating bushing 5. However, this places certain sliding friction requirements on the material strength and compatibility of the upper and lower floating bushings 9 and 5, requiring them to possess high strength and strong wear resistance, such as polyetheretherketone (PEEK).

[0055] In this embodiment, the gear pump housing 4 and the gear pump end cover 13 are fixed by a plurality of hexagon socket head cap screws 8. Both the gear pump housing 4 and the gear pump end cover 13 are provided with connection holes corresponding to the hexagon socket head cap screws 8. Specifically, four hexagon socket head cap screws 8 are used, and the four hexagon socket head cap screws 8 are respectively located at the four corners of the gear pump housing 4 and the gear pump end cover 13.

[0056] In this embodiment, the upper edge of the gear pump housing 4 is provided with a housing sealing groove, and an end cover sealing ring 14 is provided in the housing sealing groove to enhance the sealing performance between the gear pump housing 4 and the gear pump end cover 13.

[0057] In this embodiment, a lower sealing ring groove is provided on the bottom of the inner surface of the gear pump housing 4, and a lower irregular sealing ring 7 is provided in the lower sealing ring groove.

[0058] Similarly, the lower port of the gear pump end cover 13 is provided with an upper sealing ring groove, and an upper irregular sealing ring 12 is provided in the upper sealing ring groove.

[0059] The lower irregular sealing ring 7 and the upper irregular sealing ring 12 are also figure-eight shaped sealing rings. The lower irregular sealing ring 7 and the upper irregular sealing ring 12 should simultaneously meet the requirements for end face sealing and oil port sealing, and to a certain extent, they can generate pre-pressure on the lower floating bushing 5 and the upper floating bushing 9, so that they press the drive gear 15 part tightly to prevent excessive internal leakage.

[0060] Furthermore, multiple blind holes are provided on the lower inner surface of the gear pump housing 4 and the upper inner surface of the gear pump end cover 13. Each blind hole contains a spring, and the end of the spring away from the bottom of the blind hole can be used to abut against the lower floating bushing 5 or the upper floating bushing 9. The purpose is to provide a certain preload to the lower floating bushing 5 or the upper floating bushing 9, prevent excessive internal leakage of the gear pump housing 4, and improve the volumetric efficiency of the device.

[0061] In this embodiment, a relief valve mounting structure is provided between the pre-pressure oil passage 23 and the constant pressure oil passage 24. This structure is used to install the relief valve, and its specific shape must match the installed relief valve. Both the pre-pressure oil passage 23 and the constant pressure oil passage 24 are connected to the relief valve mounting structure. The structure also includes an overflow pipe outlet and a relief valve interface. The overflow valve interface is used to install the relief valve, and the overflow pipe outlet is used to discharge overflowing hydraulic oil. This is basic common sense regarding existing relief valves and will not be elaborated further. When the relief valve is not in use, an overflow pipe outlet plug 10 can be detachably connected to the overflow pipe outlet, and an overflow valve interface plug 11 can be detachably connected to the relief valve outlet, thereby achieving a sealing effect inside the device and preventing external impurities from entering.

[0062] In this embodiment, a driven shaft is provided through the center of the driven gear 6, and an axial channel is provided through the center of the driven shaft.

[0063] The gear pump end cover 13 has an upper end face leakage oil passage 21 on the inner top side. The upper end of the axial channel is connected to the upper end of the upper end face leakage oil passage 21. The gear pump housing 4 has a lower end face leakage oil passage 22 on the inner lower surface. The lower end of the axial channel and the lower pressure oil hole can be connected to the lower end face leakage oil passage 22.

[0064] In actual use, hydraulic oil may leak from the upper floating bushing 9, gear pump end cover 13, and upper special-shaped seal ring 12. This leaked hydraulic oil will flow into the axial channel through the upper end face leakage oil passage 21, then into the lower end face leakage oil passage 22, and finally flow back into the lower pressure oil hole from the lower end face leakage oil passage 22.

[0065] In this embodiment, as Figure 10 As shown, oil suction grooves 20 are provided on the side of the upper floating bushing 9 and the lower floating bushing 5 near the meshing and disengagement point of the driving gear 15 and the driven gear 6, in order to help to fully absorb oil and balance the radial unbalanced force. The technology of opening and applying the oil suction grooves 20 is common knowledge and conventional technology in the art, so it will not be described in detail.

[0066] In this embodiment, the active cycloidal gear shaft 1 and the cycloidal gear are an integral structure. However, once the active cycloidal gear shaft 1 in this structure moves axially, the cycloidal gear will move along with it, which can easily lead to wear, failure and other problems.

[0067] Or, such as Figure 15As shown, a pin 16 is perpendicularly inserted through the driving cycloidal gear shaft 1. The inner ring of the cycloidal gear has a sliding groove, and one end of the pin 16 extends into the sliding groove, thus forming a sliding key connection. The advantage of this design is that when the driving cycloidal gear shaft 1 moves axially under the action of external force, the cycloidal gear connected to it will not move axially because of the sliding key connection with the driving cycloidal gear shaft 1. This ensures that the cycloidal gear is always meshed with the driving gear 15, thereby extending its service life.

[0068] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A high-volume-efficiency combined gear pump, characterized in that: The system includes a gear pump housing (4), with a gear pump end cover (13) connected to the upper opening of the gear pump housing (4). A driving cycloidal gear shaft (1) is rotatably connected inside the gear pump housing (4). One end of the driving cycloidal gear shaft (1) extends out of the gear pump housing (4). A cycloidal gear is provided on the outer wall of the driving cycloidal gear shaft (1), and a driving gear (15) is provided on the outer side of the cycloidal gear. The cycloidal gear meshes with the inner ring teeth of the driving gear (15), and the outer ring teeth of the driving gear (15) mesh with the outer ring teeth of the driven gear (6). The upper ends of the driving gear (15) and the driven gear (6) are provided with upper floating bushings (9), and the upper floating bushings (9) are provided with upper oil pressure holes. The lower ends of the driving gear (15) and the driven gear (6) are provided with lower floating bushings (5), and the lower floating bushings (5) are provided with lower oil pressure holes. The upper oil pressure holes and the lower oil pressure holes are respectively located on both sides of the driving cycloidal gear shaft (1). The upper floating bushings (9) and the lower floating bushings (5) can slide relative to the driving cycloidal gear shaft (1). The gear pump housing (4) has an oil inlet (18) and an oil outlet (19) on its outer wall. The oil inlet (18) is located below the oil outlet (19). The oil inlet (18) can communicate with the lower pressure oil hole. Both the lower pressure oil hole and the upper pressure oil hole can communicate with the gap between the cycloidal gear and the driving gear (15). The gear pump end cover (13) has a pre-pressure oil passage (23) and a constant pressure oil passage (24). An overflow valve can be provided between the pre-pressure oil passage (23) and the constant pressure oil passage (24). The end of the pre-pressure oil passage (23) away from the overflow valve is connected to the upper pressure oil hole. The end of the constant pressure oil passage (24) away from the overflow valve is connected to the meshing and disengagement point of the driving gear (15) and the driven gear (6). The meshing and merging point of the driving gear (15) and the driven gear (6) is connected to the oil outlet (19). The hydraulic oil in the gap between the cycloidal gear and the driving gear (15) will flow into the upper pressure oil hole, and the hydraulic oil in the upper pressure oil hole will flow into the pre-pressure oil passage (23). The hydraulic oil in the pre-pressure oil passage (23) will flow through the overflow valve to the constant pressure oil passage (24). The hydraulic oil flowing out of the constant pressure oil passage (24) will enter the meshing disengagement point of the driving gear (15) and the driven gear (6).

2. The high volumetric efficiency combined gear pump according to claim 1, characterized in that: The lower end of the gear pump housing (4) is provided with a shaft through hole, and a connecting flange is provided at the shaft through hole. The connecting flange is provided with multiple fixing thread holes. The outer side of the active cycloidal gear shaft (1) is provided with a lip seal (3), the inner side of the connecting flange is provided with a retaining ring groove, and an elastic retaining ring (2) is provided in the retaining ring groove. The elastic retaining ring (2) abuts against the lip seal (3).

3. The high volumetric efficiency combined gear pump according to claim 1, characterized in that: Sliding bearings are provided between the active cycloidal gear shaft (1) and the upper floating bushing (9) as well as between the active cycloidal gear shaft (1) and the lower floating bushing (5).

4. The high volumetric efficiency combined gear pump according to claim 1, characterized in that: The gear pump housing (4) and the gear pump end cover (13) are fixed by a number of internal hexagonal head screws (8).

5. The high volumetric efficiency combined gear pump according to claim 1, characterized in that: The upper edge of the gear pump housing (4) is provided with a housing sealing groove, and an end cap sealing ring (14) is provided in the housing sealing groove.

6. The high volumetric efficiency combined gear pump according to claim 1, characterized in that: The bottom of the inner surface of the gear pump housing (4) is provided with a lower sealing ring groove, and a lower special-shaped sealing ring (7) is provided in the lower sealing ring groove. The gear pump end cover (13) is provided with an upper sealing ring groove at the lower port, and an upper special-shaped sealing ring (12) is provided in the upper sealing ring groove.

7. The high volumetric efficiency combined gear pump according to claim 1, characterized in that: An overflow valve mounting structure is provided between the pre-pressure oil passage (23) and the constant pressure oil passage (24). The overflow valve mounting structure is used to install the overflow valve. The pre-pressure oil passage (23) and the constant pressure oil passage (24) are both connected to the overflow valve mounting structure. The overflow valve mounting structure is also provided with an overflow pipe outlet and an overflow valve interface. An overflow pipe outlet plug (10) can be detachably connected to the overflow pipe outlet, and an overflow valve interface plug (11) can be detachably connected to the overflow valve outlet.

8. The high volumetric efficiency combined gear pump according to claim 1, characterized in that: The driven gear (6) has a driven shaft passing through its center, and the driven shaft has an axial channel at its center; the gear pump end cover (13) has an upper end face leakage oil passage (21) on its inner top side, and the upper end of the axial channel is connected to the upper end of the upper end face leakage oil passage (21); the gear pump housing (4) has a lower end face leakage oil passage (22) on its inner lower surface, and the lower end of the axial channel and the lower side pressure oil hole are both connected to the lower end face leakage oil passage (22).

9. The high volumetric efficiency combined gear pump according to claim 1, characterized in that: Both the upper floating bushing (9) and the lower floating bushing (5) are provided with oil suction grooves (20) on one side.

10. The high volumetric efficiency combined gear pump according to claim 1, characterized in that: The active cycloidal gear shaft (1) and the cycloidal gear are an integral structure; Alternatively, a pin (16) is vertically inserted through the active cycloidal gear shaft (1), the inner ring of the cycloidal gear is provided with a groove, and one end of the pin (16) extends into the groove.

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